Is “Gravity” a great film or the greatest film? Hyper-buzzed and destined for both technical and artistic awards aplenty, there’s no arguing that Alfonso Cuaron’s first film in seven years — since the harrowing but financially lacking “Children of Men” — is an original. Sandra Bullock and George Clooney, the only actors we ever clearly see, play astronauts whose routine repair mission is thwarted when they’re pelted by debris from a satellite crash.

The minimalist plot doesn’t matter. What matters is that the digital filmmaking, aided by 3-D (and in some theaters, IMAX), thoroughly conveys the feeling of weightlessness, as well as the lack of autonomy that comes with it. Cuaron created genuinely thrilling long takes in “Children of Men.” Here, he goes further. His camera (or “camera”) floats freely through space or into the point-of-view of its two characters as they lose control, drifting or spinning (or both) as they head to potential death every few minutes. The experience is like an amusement park ride, not so much a roller coaster as one of those motion simulators where the seats rock and jiggle as the screen in front of you creates the illusion of movement.

Alas, the film overall is “merely” great. For an hour, it doesn’t matter that it’s not really about anything apart from sheer sensation. (That, and an adherence to realism — bits of sound in the vacuum of space being a rather glaring exception.) Cuaron actually finds something genuinely new with cinema, and at its heart this is a survivalist tale — like “All Is Lost,” the sea film that one-ups this one’s bare-bones cast by only featuring Robert Redford — crossed with an avant-garde film. (In a way, it's a much, much, much more accessible/mainstream version of Michael Snow’s epic “La Region Centrale,” in which a camera on a twisting track spends three hours shooting a remote landscape from endlessly fresh angles.)

But there’s always a temptation to do something more than shtick. Exactly when it seems like it couldn’t keep this up for an entire movie — even if that would be wonderful — the hour mark brings a silly scene that spoils the hard-earned mood. It tries to rebound, but what follows only underlines the smallness of its scope. There’s nothing wrong with “Gravity” being about something more than just Bullock and Clooney bumming around space, in a beautiful dance with Cuaron’s filmmaking. But if it must be about something, then it should be something big, not the half-assed quasi-religious claptrap it ultimately becomes.